B.G 3.14, 15 and 16

अन्नाद् भवन्ति भूतानि पर्जन्यादन्नसम्भवः। यज्ञाद् भवति पर्जन्यो यज्ञः कर्मसमुद्भवः ॥१४॥

कर्म ब्रह्मोद्भवं विद्धि ब्रह्माक्षरसमुद्भवम्। तस्मात् सर्वगतं ब्रह्म नित्यं यज्ञे प्रतिष्ठितम् ॥१५॥

एवं प्रवर्तितं चक्रं नानुवर्तयतीह यः। अघायुरिंद्रियारामो मोघं पार्थ स जीवति ॥१६॥

From food comes beings, and food becomes possible from rains. The rains are produced from 'Yajna' and it is 'Yajna' that is the source of the prescribed duties. The actions have their origin in Brahman, and understand that the Vedas also arose simultaneously from that same Brahman. Therefore, the all pervading Brahman is always situated in the 'Yajna'. O Partha, he who does not adhere to the cycle thus set in motion, who only delights in the senses, is sinful, and lives in vain.

Gīta Tātparya 3.14 to 16

Elaboration of the Yajna cycle with the usage of 'Akshara' to mean Vēdas is quoted as a testimonial from Narada Purana. Thus, 'Brahma' means the Brahman, and 'Akshara' means the Vēdas. This interpretation also ensures it is coherent with the prase "tasmāt sarvagataṁ brahma", i.e. "the all pervading Brahma".

जननात् परसस्यादेः पर्जन्यो मेघसन्ततिः। स यज्ञात् कर्मणः सोपि समस्तं कर्म केशवात्॥

स नित्योऽप्यक्षरततिरूपाद्वाक्यादि्ध गम्यते। वाक्यमुच्चार्यते भूतैः तान्यन्नात् तच्च मेघतः॥

तस्मात् सर्वगतो विष्णुः नित्यं यज्ञे प्रतिष्ठितः। एवं प्रवर्तितं चक्रं नानुवर्तयतीह यः। स पापो विश्वहन्तृत्वात् नरके मज्जति ध्रुवम्॥

The vegetation is born from the continuous series of clouds through rain. Similarly, from that lord Keshava, through 'Yajna', all duties are performed. Even though He is eternal, he is understood through the statements in the form of 'akshara' i.e. Vēdas, by the utterances of those sentences by beings, the way food is produced from the clouds. Therefore, the all pervading lord Vishnu is eternally established in 'Yajna'. That sinner who does not adhere to the cycle thus set is motion, because of being the destroyer of the world, certainly sinks to hell.

वाचिको मानसो यज्ञो न्यासिनां तु विशेषतः। वनस्थस्याक्रतुः यज्ञः क्रत्वादिर्ग्रहिणोखिलः॥

शुश्रूषाद्यात्मको यज्ञो विहितो ब्रह्मचारिणः। विद्याभयादिदानं च सर्वेषामपि सम्मतम्॥

गृहिणो वित्तदानं तु वनस्थस्यान्नपूर्वकम्। सर्वैः कार्यं तपो घोरमिति सर्वे त्रिकर्मिणः॥

इति नारदीये।

The sacrifice of speech and mind is meant especially for the renounced order. The forest dwellers, i.e. who are retired, should keep their sacrifices light by offering food that involved no killing. Serving others by physical service is the sacrifice recommended for celibate students. Studies and other such activities are the agreeable sacrifice to all. House holder must give wealth as charity and the retired person by offering food first. All must practice penance. Thus, three orders, i.e. student, householder, and retired, must sacrifice through studies, charity, and penance.

- states Naradiya Purana

ब्रह्माक्षरशब्दार्थयोः व्यत्यासे तस्मात् सर्वगतं ब्रह्मेति प्रत्यभिज्ञाविरोधः चक्रप्रवेशश्च ॥१४-१६॥

The meaning of the words 'Brahma' and 'Akshara' must be differentiated, with 'Brahma' to mean the Omnipresent lord, and the other to mean that (Vedas) which provides entry into the cycle (of Yajna). Thus, it becomes coherent with the phrase "tasmāt sarvagataṁ brahma", i.e. "the all pervading Brahma".